Figure 6.

Summary of the plasticity induced by an acute cocaine injection in animals withdrawn from daily cocaine or saline treatments. The illustration is not a drawing of a biological sample but provides a generalized view of how spine morphology is altered by withdrawal from daily cocaine or saline and a subsequent acute cocaine challenge. A, In daily saline-withdrawn animals, the only effect occurred after 360 min after acute cocaine administration and consisted of a coordinated increase in spine density PSD proteins and amplitude of field potentials elicited by prefrontal cortex stimulation. B, In daily cocaine-withdrawn subjects, acute cocaine elicited rapid bidirectional changes in spine morphology over the first 2 h after acute cocaine injection that were associated with a reduction in field amplitude. Actin binding proteins revealed an increase in branching and gradual decrease in actin content due to increases in cofilin. Although spine morphology appeared to normalize by 360 min after injection, the continued reduction in actin and NMDA2A was paralleled by an enduring decrease in field amplitude. —, No change; up arrow, increase; down arrow, decrease; arrow with line, strong trend toward change.